Airport pavement indicia and signs provide information that is useful to a pilot during takeoff, landing, and taxiing. Generally airport indicia are grouped into four categories: runway indicia, taxiway indicia, holding position indicia, and other indicia. Indicia for runways are white. Indicia for taxiways, areas not intended for use by aircraft (closed and hazardous areas), and holding positions (even if they are on a runway) are yellow. Indicia for heliports are white with the exception of medical helicopter areas which are white with a red cross.
Presently much of the runway and taxiway information is painted onto the concrete or asphalt. This paint may last for several weeks or several months depending on the amount of use, the size of the aircraft traffic using it and/or severity of environmental conditions.
It has been found that uniformity in airport indicia and signs from one airport to another enhances safety and improves efficiency. FAA Standards AC 150/5340-1 “Standards for Airport Indicia” and AC 150/5340-18 “Standards for Airport Sign Systems” are both references that define the minimum requirements for airport indicia and signage. Non-maintenance of painted indicia may allow indicia to become deteriorated to a point where the information being conveyed is confusing or illegible.
Runway indicia may also be divided into the following groups: visual runway indicia, non-precision instrument indicia and precision instrument indicia. Additional indicia are required for runway lengths over 4000 feet and for runways serving international commercial transports.
Maintenance of the painted surfaces require that runways and taxiways be shut down while the surface is prepared, paint applied and for curing time. Maintenance of a particular runway may impact the holding and taxiways of adjacent or intersecting pavement. The pavement warnings of adjacent or intersecting pavement must change to denote changes in holding areas, and thresholds to avoid ground collisions with other aircraft.
Presently many airports have allocated budgets for painting the warning, identification and directional indicia. Painting the runway surfaces is performed on a rotational basis of about every three weeks depending on the volume and size of the aircraft traffic. Although the painting of the runway surface is relatively quick, the runway traffic needs to be rerouted to other runways causing flight delays while the painting and drying of the painting occurs. It also is expensive in that full time painting crews are continually rotating from runway to runway.
Ground safety remains a problem at busy airports across the United States and the world. The movement of aircraft in and around busy airports along taxiways between terminal gates and runways presents numerous opportunities for runway incursions, particularly when visibility is poor. A runway incursion is the entry of an aircraft without clearance onto an active runway from an adjacent ramp or taxiway, for which there is a great deal of risk of collision with a landing or departing aircraft. Incursions are often the inadvertent result of pilot disorientation caused by poor visibility.
As recently as Aug. 26, 2006, Comair Flight 5191 crashed about half a mile past the end of a runway at the Lexington, Ky. airport, killing 49 of the 50 people onboard. The plane took off on runway 26, not runway 22 where it was assigned. It was an early morning flight with overcast skies and a slight rain. The NTSB probe is focusing their investigation on recent construction work at the Lexington airport, lighting and the indicia on the taxiways and runways.
This does not include incidents such as taxiway collisions or near misses resulting from vehicle operators mistaking one taxiway for another. Runway incursions and other taxiway incidents can still represent inconvenience and expense even when a ground collision does not result. To return an aircraft to a path from which it has strayed requires a considerable expenditure of time and fuel, and a compromise to the safety of all involved.
In addition to the need for runway signage that is relatively simply and quick to apply and that exhibits exceptional wear characteristics as well as allowing for delayed intervening scheduled maintenance, thereby assisting with the reduction of the cost of maintenance, delayed flights and confusion due to runway rerouting, the signage should also be highly retroreflective and skid resistant.
Specifically, the need for high retroreflectivity nighttime visinility has been increased to near or about 1000 millicandellas/m2/lux (mcd) and this high retroreflectivity requires glass beads that must remain at or near the top surface of the signage to ensure that the retroreflectivity is maintained during and after installation. To create the proper composition requires a specific composition of the alkyd-based preformed thermoplastic composite which is one embodiment of the present disclosure.